Fuel cells have been used as a power source in many applications. For example, fuel cells have been proposed for use in electrical vehicular power plants to replace internal combustion engines. In proton exchange membrane (PEM) type fuel cells, hydrogen is supplied to the anode of the fuel cell, and oxygen is supplied to the cathode. PEM fuel cells include a membrane electrode assembly (MEA) comprising a thin, proton transmissive, non-electrically conductive solid polymer electrolyte membrane having the anode catalyst on one of its faces and the cathode catalyst on the opposite face. The MEA is sandwiched between a pair of electrically conductive elements which serve as current collectors for the anode and cathode, and contain appropriate channels and/or openings therein for distributing the fuel cells gaseous reactants over the surfaces of the respective anode and cathode catalyst. A typical PEM fuel cell and its membrane electrode assembly (MEA) are described in U.S. Pat. Nos. 5,272,017 and 5,316,871 issued respectively Dec. 21, 1993 and May 31, 1994 and assigned to General Motors Corporation.
The term “fuel cell” is typically used to refer to either a single cell or a plurality of cells depending on the context. A plurality of individual cells are commonly bundled together to form a fuel cell stack. Each cell within the stack comprises the MEA described earlier, and each such MEA provides its increment of voltage. Typical arrangements of multiple cells in a stack are described in U.S. Pat. No. 5,763,113 assigned to General Motors Corporation, and which is herein incorporated by reference.
During fuel cell system start-up, a compressor is often utilized to provide compressed air or oxygen to the fuel cell cathode inlet while hydrogen is introduced to the fuel cell anode inlet. Many fuel cell systems currently use large battery packs to start and operate the compressor before output power is available from the fuel cell stack. The large battery pack often is utilized with various DC/DC converters to provide the high voltage necessary for the compressor. Usually, one or more DC/DC converters are needed to get the battery voltage up to the stack level, then another DC/DC converter is needed to get the voltage from the stack level up to the compressor motor level. The large battery pack and DC/DC converters contribute significantly to the weight, volume, and cost of the fuel cell system. Thus, it is desirable to provide a simplification of the fuel cell system as well as reducing the mass, volume and cost of the system.